In the oil industry, the water-liquid-ratio (wlr) is an important measurement of the output flowing from a well and for wells producing a three-phase flow (gas, oil and water) separator systems are used to separate the gas, oil and water into individual streams to simplify the wlr measurement. However separator systems are heavy, bulky, costly and prone to failure and obtaining three separate streams for each component can be complicated and costly.
Where the liquid, i.e. water and oil, is not separated and metering is performed on the multi-phase flow, the measurement of the wlr can be very difficult, particularly when the volume fraction of gas in the line is high. For example, where the wlr is 10% in a multi-phase flow with 90% gas, then 1% of the total volume is water, 9% is oil and 90% is gas. Measurement of the wlr in a multi-phase flow requires detecting the presence of the 1% by volume of water, whereas if all the gas is removed leaving an oil-water flow, measurement of the wlr requires detecting the presence of the 10% by volume of water. Removing gas from the multi-phase stream to produce a liquid-rich stream therefore makes measurement of the wlr easier.
Hydrocyclones are used to produce a liquid-rich stream from a multi-phase flow. However these systems tend to be large and result in the liquid and gas phases travelling in opposite directions which can cause problems with pipe layout.
It is an aim of the present invention to produce a device for obtaining a liquid-rich stream without the disadvantages associated with the prior art, and also aims to provide a device for retrofitting to existing flow meters to increase their range of operation.